Incinerator draft control and vent valve



June 3, 1969 H. E. TAYLOR ET AL 3,

INCINERATOR DRAFT CONTROL AND VENT VALVE Sheet Filed Dec. 28. 1967 R mm T Y L A R W m W x 02w ATTORNEY June 3, 1969 H. E. TAYLOR ET AL 3,

INCINERATOR DRAFT CONTROL AND VENT VALVE Sheet 2 of 2 Filed D80. 28, 1967 FIG. 3

FIG. 2

INVENTOR. 1

HERBERT E. TAYLOR DAVID R. PEARL ATTORNEY United States Patcnt O 3,447,493 INCINERATOR DRAFAILCgNTROL AND VENT V V Herbert E. Taylor, Longmeadow, Mass., and Daw'd R. Pearl, West Hartford, Conn., assignors to Combustion Engineering, Inc., Windsor, Conn., a corporation of Delaware Filed Dec. 28, 1967, Ser. No. 694,209 Int. Cl. F23g 5/00; F231 11/00, 13/04 US. Cl. 1l07 2 Claims ABSTRACT OF THE DISCLOSURE Background of the invention Because of air pollution, it has become desirable to clean the gases exiting from refuse incinerators. One method of accomplishing this is to pass the hot, dust-laden gases exiting from the incinerator through a wet scrubber where the foreign matter is removed from the gas stream and the temperature is considerably lowered. The cleaned, cooled gases leaving the wet scrubber pass through a double walled construction of the incinerator performing the dual function of maintaining the furnace walls cool and heating the gases to a high enough temperature so that there will be no visible steam plume when the gases are exhausted to atmosphere. In such a system, there is the danger of overheating of both the furnace walls and the wet scrubber equipment, if for some reason the Water sprays within the wet scrubber fail.

Summary of the invention A vent valve is positioned in the ductwork between an incinerator exhaust and a wet scrubber. Upon the sensing of a predetermined maximum gas temperature leaving the Wet scrubber, the valve is actuated so as to close the duct and also opens both the furnace and the wet scrubber to atmosphere.

Brief description of the drawing FIGURE 1 is a sectional side View of an incinerator and wet scrubber arrangement incorporating the vent valve of our invention;

FIGURE 2 is an enlarged side view of the vent valve shown in FIGURE 1, the valve being shown in its open position; and

FIGURE 3 is a sectional view of the vent valve taken on lines 3--'3 of FIGURE 2.

Description of the preferred embodiment Looking now to FIGURE 1, is an incinerator for burning refuse introduced into the furnace through opening 12. Air to support combustion of the refuse on grate 14 is supplied by fan 17 and duct 19. Ash is discharged from the rear of the grate into ashpit 15. The hot gases, laden with ash particles, flow upwardly in the furnace, around arch 16, and exit through the furnace outlet 18 into duct 22. The gases then flow through wet scrubber 20, where they are subjected to a series of scrubbing sprays.

The ash is entrained by the water droplets, and thus separated from the gas stream and deposited in the scrub- 3,447,493 Patented June 3, 1969 her sump. The cleaned, cool, saturated gases leave the wet scrubber by means of induced draft fan 21 and duct 24, and enter plenum duct or manifold 26, which encircles the upper portion of the furnace.

The upper portion of the incinerator is of double-wall construction, there being an inner refractory lined wall 28 and an outer metal casing 30. Duct 26 feeds the cleaned, cool, saturated gases into the space 31 around the entire periphery of the incinerator. The gases are then exhausted to the atmosphere through upper outlet 32. In passing the gases through space 31 a two-fold advantage is gained. Firstly, the gases absorb heat from the refractory walls 28, preventing them from becoming overheated, which could cause spalling or cracking. Secondly, the temperature of the gas is raised. This makes them more buoyant and because the moisture in the gases then represents a lower percentage of saturation, there is less likelihood that a visible steam plume will be seen in the gases exiting from outlet 32.

Positioned Within duct 22 upstream of the wet scrubber 20 is the control and vent valve 40. This damper valve can be actuated in response to two conditions. One is the pressure within the incinerator furnace 10, as sensed by pressure sensing device 42 located in the upper portion of the incinerator. The second is the temperature of the cleaned cooled gases leaving the wet scrubber 20 as sensed by the temperature sensing device 46 located in duct 24.

During normal operation of the incinerator 10, it is desirable to maintain it at a predetermined partial vacuum. This enables the refuse to be burned without smoke escaping from the furnace doors, joints and seams (i.e. an undesirable condition called outgassing). However, too great a vacuum, which could result from burning refuse of low combustibility, is also undesirable because of the increase of air infiltration through the unavoidable leakage points which would tend further to cool the fire. When too great a vacuum is created in the incinerator by fan 21, this condition is sensed by pressure sensor 42, which sends a signal to motor drive 44 of valve 40, moving it in a direction to allow more air to enter duct 22. When sensor 42 detects an increase in pressure in the incinerator, valve 40 is moved in a closing direction, decreasing the amount of entering duct 22 from the atmosphere.

In the event of failure of the water supply to the wet scrubber, or failure of the induced draft fan 21, the temperature of the gases would increase substantially. This could cause considerable damage to the upper walls of the furnace, and to the wet scrubber. In order to safeguard against this, temperature sensing device 46 is positioned in duct 24. When a predetermined maximum temperature is sensed, 46 sends a signal to motor drive 44 of vent valve 40, moving it to its fully open position (as shown in FIG- URE 2) and holding it in that position. During normal operation temperatures of 250-300 F. exist downstream of the wet scrubber. A trip out temperature of 400 F. could be used. In this position, valve 40 prevents any hot gases flowing from the furnace to enter the wet scrubber. The gases from the furnace exit to the atmosphere through opening 50 in baffle arrangement 48. Simultaneously, atmospheric air can enter through opening 52 and flow to the wet scrubber 20. The purpose of the bafile arrange ment 48 is to prevent the hot furnace gases which are being vented on the left-hand side of damper 40 from passing right around the damper and being drawn back in on the right-hand side.

From the above it can be seen that when the vent valve 40 is actuated by temperature sensing device 46, it prevents gases from the furnace from entering the wet scrubher. It also permits relatively cold atmospheric 'air to enter through opening 52 and flow through the wet scrubber and the double walls of the furnace. This is true even when the cause in rise of temperature is due to failure of fan 21. Air will move through the wet scrubber and furnace walls due to the chimney effect; i.e., hot air being lighter tends to How upward, thus drawing in cold air at the bottom or in this instance through opening 52. This will prevent overheating and damage of both the furnace walls and the wet scrubber. During this emergency venting period, the operator can stop feeding refuse to the incinerator and repair the water spray or fan 21. When this is accomplished, vent valve 40 can be reset in its closed position and the incinerator put back into operation.

While the preferred embodiment has been illustrated and described, it is to be understood that the invention should not be limited thereto.

What We claim is:

1. In combination, a furnace for burning fuel therein, said furnace having 'an outlet through which the hot, dirty combustion gases leave the furnace, scrubber means hav- H ing an inlet and an outlet, duct means connecting the furnace outlet to the scrubber means inlet, said duct means containing valve means therein, control means which in response to the sensing of a predetermined maximum temperature downstream of the scrubber means actuates the valve means to move it to such a position that it closes the duct means, preventing flow of combustion gases from the furnace to the scrubber means, and

opens both the furnace outlet and the scrubber means to the atmosphere.

2. In combination, a furnace for burning fuel therein, having spaced, double walls, said furnace having an outlet through which the hot, dirty combustion gases leave the furnace, scrubber means having an inlet and an outlet, duct means connecting the furnace outlet to the scrub- 'ber means inlet, the outlet of the scrubber means being connected to the space between the double walls of the furnace, said duct means containing valve means therein, control means which in response to the sensing of a predetermined maximum temperature downstream of the scrubber means actuates the valve means to move it to such a position that it closes the duct means, preventing flow of combustion gases from the furnace to the scrubber means, and opens both the furnace outlet and the scrubber means to the atmosphere.

References Cited UNITED STATES PATENTS 2,242,653 5/1941 Maxwell 11O119 X 2,729,301 1/1956 Ekstrom 110-l 19 3,320,906 5/ 1967 Domahidy.

JAMES W. WESTHAVER, Primary Examiner.

US. Cl. X.R. 110-119; 126-293 

